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After go1.16, go will use module mode by default, even when the repository is checked out under GOPATH or in a one-off directory. Add go.mod, go.sum to keep this repo buildable without opting out of the module mode. > go mod init github.com/mmcgrana/gobyexample > go mod tidy > go mod vendor In module mode, the 'vendor' directory is special and its contents will be actively maintained by the go command. pygments aren't the dependency the go will know about, so it will delete the contents from vendor directory. Move it to `third_party` directory now. And, vendor the blackfriday package. Note: the tutorial contents are not affected by the change in go1.16 because all the examples in this tutorial ask users to run the go command with the explicit list of files to be compiled (e.g. `go run hello-world.go` or `go build command-line-arguments.go`). When the source list is provided, the go command does not have to compute the build list and whether it's running in GOPATH mode or module mode becomes irrelevant.
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221 lines
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<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: Number Parsing</title>
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<link rel=stylesheet href="site.css">
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</head>
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<script>
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onkeydown = (e) => {
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if (e.key == "ArrowLeft") {
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window.location.href = 'random-numbers';
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}
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if (e.key == "ArrowRight") {
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window.location.href = 'url-parsing';
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}
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}
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</script>
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<body>
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<div class="example" id="number-parsing">
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<h2><a href="./">Go by Example</a>: Number Parsing</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Parsing numbers from strings is a basic but common task
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in many programs; here’s how to do it in Go.</p>
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</td>
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<td class="code empty leading">
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<a href="http://play.golang.org/p/ZAMEid6Fpmu"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>The built-in package <code>strconv</code> provides the number
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parsing.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"strconv"</span>
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<span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>With <code>ParseFloat</code>, this <code>64</code> tells how many bits of
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precision to parse.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">f</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nx">ParseFloat</span><span class="p">(</span><span class="s">"1.234"</span><span class="p">,</span> <span class="mi">64</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">f</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>For <code>ParseInt</code>, the <code>0</code> means infer the base from
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the string. <code>64</code> requires that the result fit in 64
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bits.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">i</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nx">ParseInt</span><span class="p">(</span><span class="s">"123"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">64</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">i</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>ParseInt</code> will recognize hex-formatted numbers.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">d</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nx">ParseInt</span><span class="p">(</span><span class="s">"0x1c8"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">64</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">d</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>A <code>ParseUint</code> is also available.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">u</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nx">ParseUint</span><span class="p">(</span><span class="s">"789"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">64</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">u</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p><code>Atoi</code> is a convenience function for basic base-10
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<code>int</code> parsing.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">k</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nx">Atoi</span><span class="p">(</span><span class="s">"135"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">k</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Parse functions return an error on bad input.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">_</span><span class="p">,</span> <span class="nx">e</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nx">Atoi</span><span class="p">(</span><span class="s">"wat"</span><span class="p">)</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">e</span><span class="p">)</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="gp">$</span> go run number-parsing.go
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<span class="go">1.234</span>
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<span class="go">123</span>
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<span class="go">456</span>
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<span class="go">789</span>
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<span class="go">135</span>
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<span class="go">strconv.ParseInt: parsing "wat": invalid syntax</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Next we’ll look at another common parsing task: URLs.</p>
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</td>
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<td class="code empty">
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</td>
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</tr>
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</table>
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<p class="next">
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Next example: <a href="url-parsing">URL Parsing</a>.
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</p>
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<p class="footer">
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/number-parsing">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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</p>
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</div>
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<script>
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</body>
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